A device for punching blanks out of a flat sheet, in particular packaging blanks consisting of cardboard or corrugated cardboard, using a punching tool that is mounted in a carrier plate and projects beyond the plate in the form of a blade or cutting line, in addition to profiled strips, consisting of a material of limited flexibility, which flank the tool. A rail-type profiled channel consisting of a rigid material is located on the carrier plate, running parallel to the punching tool on each side of the longitudinal faces of the latter and one cross-sectional area of the profiled strip is inserted into the profiled channel in a positive fit. In addition, at least one lateral face of the cross-section of the profiled strip has a protuberant base.